A color liquid crystal display device which is currently widely used includes a color filter arranged in a sub-pixel (dot). Color filters of three primary colors of light, i.e., red (R), green (G), and blue (B), are arranged in sub-pixels in a specific pattern, typically. Thus, according to the color liquid crystal display device, one pixel is composed of three sub-pixels of R, G, and B. This pixel serves as the minimum constitutional unit of a screen to provide color display. The colors of the color filters, that is, the combination of the colors of the sub-pixels are not limited to the combination of R, G, and B. A combination of cyan (C), magenta (M), and yellow (Y) or another combination may be employed. As the array of the color filters, a stripe array, a delta array, and a mosaic array have been known.
A common color liquid crystal display device has a structure in which a liquid crystal layer is formed between a pair of substrates, and a plurality of color filter layers are formed on either one of the pair of substrates. For example, an active matrix driving liquid crystal display device has a structure in which an active matrix substrate including circuit elements such as a pixel electrode and a thin film transistor (TFT) (hereinafter, also referred to as a “TFT substrate”) and a counter substrate including a counter electrode and a color filter layer and the like are arranged with a liquid crystal layer therebetween. The counter substrate including the color filter layer is often called color filter substrate.
Production processes of such a color liquid crystal display device include a step of attaching and fixing the color filter substrate to the TFT substrate. In this case, a spacer is arranged between the color filter substrate and the TFT substrate in order to keep a thickness of the liquid crystal layer (hereinafter, also referred to as a “cell gap”) uniform. However, in a television receiver field and the like, degradation in display qualities, due to the spacer, becomes a problem with an improvement in display qualities of the liquid crystal display device.
Bead spacers or rod spacers with a specific diameter are sprayed on the color filter substrate or TFT substrate surface, thereby arranging the spacers between the color filter substrate and the TFT substrate, conventionally. However, in this case, it is difficult to arrange the spacers on the entire display surface of the liquid crystal display device at a uniform density. Therefore, the cell gap is not uniform, or the spacers gather, which often causes display defects. In addition, due to the spacer arranged in the sub-pixel, the aperture ratio is substantially reduced or the spacer is observed as a luminescent spot.
A method in which a spacer is selectively arranged in a specific region outside a sub-pixel, typically arranged in a black matrix or a region shielded by a wiring arranged on a TFT substrate has been developed. For example, a method in which a column spacer is arranged in a specific region on a color filter substrate and/or a TFT substrate by a photolithography process using a photosensitive resin (also referred to as a “photoresist”) has been practically used.
The following liquid crystal display device is disclosed, for example (for example, refer to Patent Document 1). A plurality of column spacers for regulating a distance between the TFT substrate and the color filter substrate are arranged in a region which does not transmit light between a plurality of effective pixels to have a height equal to a specific distance between the substrates. The top surfaces of these column spacers are in touch with an internal surface of the other substrate. A column spacer made of a photosensitive resin, that is, a photo spacer (hereinafter, also referred to as a “PS”) is arranged on the color filter substrate of this liquid crystal display device. On the TFT substrate, at apart where the PS is in contact with the TFT substrate, a gate wiring and a data wiring overlap with each other with an insulating film therebetween to generate a bulge. In addition, the following color filter (color filter substrate), is disclosed, for example (for example, refer to Patent Document 2). A foundation is formed using a black matrix layer and at least one or more kinds of colored layers of the three primary colors outside a screen, and on the foundation, a resin column (PS) is further arranged.
In addition, the following active matrix substrate is disclosed, for example (for example, refer to Patent Document 3). A column spacer is bonded to a part which has an irregular surface and has a substantially tapered cross-section, such as a gate wiring, and the column spacer has a taper angle in accordance with the tapered shape of the gate wiring. Further, the following In-Plane Switching active matrix liquid crystal display device is disclosed, for example (for example, refer to Patent Document 4). A long thin insulator bump is formed to cover a video signal wiring and serves as a spacer for determining a liquid crystal cell gap when a liquid crystal cell is assembled.
The following color filter substrate is disclosed as a technology of suppressing foaming of a liquid crystal layer at low temperatures and improving withstand load characteristics, for example (for example, refer to Patent Document 5). The color filter substrate includes two different column spacers different in height.
FIG. 17(a) is a planar view schematically showing a configuration of the color filter substrate disclosed in Patent Document 5. FIG. 17(b) is a cross-sectional view schematically showing the color filter substrate taken along line A-B in FIG. 17(a).
This color filter substrate includes column spacers 78 and 79 arranged in a region outside the sub-pixel, as shown in FIG. 17(a). In the region outside the sub-pixel of the color filter substrate 70, as shown in FIG. 17(b), a black matrix 72, color filters 73 and 74, and a common electrode 75 are stacked on a transparent substrate 71. Thereon, a photosensitive resin layer 76 and an alignment film 77 are formed. The color filter 73 and the color filter 74 adjacent thereto are different in thickness, and by this thickness, the column spacers 78 and 79 are different in height.    [Patent Document 1]    Japanese Kokai Publication No. 2000-298280    [Patent Document 2]    Japanese Kokai Publication No. 2001-51266    [Patent Document 3]    Japanese Kokai Publication No. He-11-174467    [Patent Document 4]    Japanese Kokai Publication No. 2004-341465    [Patent Document 5]    Japanese Kokai Publication No. 2003-84289